Using R and U values to make an efficient home
R-values and U-values are very common terms when it comes to home insulation: they are very easy to confuse, and difficult for consumers to connect with the material’s performance but they make a huge difference. Knowing what they stand for allows people to easily find R and U-values when they compare the market.
Making wise decisions and purchasing the right cost-effective materials, doors and windows, can make a huge difference to the quantity of heat energy that is consumed, and the amount of money payable to the utility companies, who are practically guaranteed to raise their prices with each passing year. Being in the know, and acting upon it also makes a huge contribution to a greener and more sustainable way of living.
R-Values In Insulation
R-value refers to thermal resistance. Essentially, it is a measure of a material’s resistance to the flow of heat via convection, conduction, and radiation, through the variable thickness of a specific material, as well as how well different materials can insulate a building. This means that the higher the number of the R-value, the more superior the insulation. Therefore, an insulator with a high R-value will be more adept at combating energy transfer, and keeping up a temperature difference across the material for an extended time. Ultimately, the higher the R-value, the more money you will save by requiring less energy to heat your home. The R-value escalates when the thickness of the insulating layer is enhanced but does not work entirely alone. This means that when calculating the wall cavity R-value you should also take into account: the insulation, wall sheathing, and internal drywall need already in place to come to the sum total. Even if the wall insulation is second-to-none, and the conduction via the insulation is removed, it does not affect the loss of heat via other components of the building including: studs, windows and doors; as well as heat loss through the exchange of flowing air.
The R-value is attained by working out the material’s thickness in square meters and then dividing it by the material’s conductivity. The resistance of each individual material found within the element are combined together to produce the total resistance. For example:
A Board of 0.022W/mk with 100mm equals 0.1M divided by 0.022 which equates to an R-Value of 4.54 meters square K/W.
U-Values With Doors, Windows and Walls
Put simply, U-value is the opposite of R-value. The U-Value is the measurement of how fast the heat transfers, this means that products with a lower U-value will be more energy efficient. The total heat transfer relates to the transference of energy via radiation and conduction. It is a measurement of thermal performance that denotes how well doors windows units, and lofts – each constructed from different materials – can insulate a building. The lower a U-value measurement is, the better the energy efficiency will be. Unlike the single building materials used for R-values, individual windows units and doors are constructed with multiple materials, and these may have different functions such as: ventilation, filtration, and the prevention of heat transference.
The U-value is attained by the use of Watts per meter squared per degree Kelvin. So to cite an example: if there is a U-value of 1.0 is produced by a wall, one square meter of the wall will allow 1 Watt to travel through it if there is a 1 degree variation in temperature present between the inside of the building and outside.
U-values in buildings run on a typical scale from a minimum of approximately 0.15 W/per meter squared kelvin for a roof with contemporary construction featuring loft insulation of 300mm thickness; to a maximum of approximately 5.0 W/per meter squared kelvin for a window with single glazing. This equates to the window allowing around thirty times more heat to travel through 1 square meter of it compared to the roof. An astounding 25% of a building’s heat is lost via an uninsulated roof space which is linked to a U-value of around 2.5 W/per meter squared kelvin, as opposed to an insulated loft space which yields a u-value of under 0.15 W/per meter squared kelvin.
A window with single glazing has a U-value of approximately 4.8 W/per square meter kelvin, whereas a window with double glazing with air between the panes with a gap of 6mm has a U-value of 3.1 W/per square meter kelvin, a gap of 12mm has a U-value of 2.8 W/per square meter kelvin, and a gap of 16mm has a U-value of 2.7 W/per square meter kelvin, and the most recent a U-value of 1.6 W/per square meter kelvin.
Using U Values and R Values To Make Your Home Warmer
The history of insulation affects many older property owners who do not realise that by applying insulation, they could ecologically transform the way their building is heated, and save a fortune in heating bills. Houses constructed prior to the 1930s have solid walls without any insulation, and it is apparent that until the mid 90s, they were left that way, meaning they demand a lot of heating to keep warm. If for example, the bricks have a 225mm thickness, the U-value will be 2.20 W/per square meter kelvin. In order to rectify this situation, and bring the U-value down to 0.2 W/per square meter kelvin, the wall must be insulated either externally or internally. If you’re planning renovations then it’s worth remembering that the age of your home is likely to have a large effect on how efficient it is. Small changes can make a huge difference, even with protected and historic buildings.
When considering ways to make your heating bills more affordable you should consider the U and R values of your home. A quick assessment of materials used can quickly reveal if your home is losing a lot of its heat. Producers are also recognising a growing demand from consumers, who want to properly understand the efficiency of their homes, leading to more information on product pages for both external doors and windows. If you can’t find these details when shopping for fittings then get in touch with your supplier, they should be able to provide you with the information you need.
Taking R and U values into account can change the way you view future renovations, saving you money in the process and helping you become more energy efficient
Many thanks to our author Kayleigh Herbertson for writing this article.